Sandwich panel, method of building such a sandwich panel, a core of such a sandwich panel, and a building built of a plurality of such sandwich panels

ABSTRACT

The invention relates to a sandwich panel, comprising: —a core, comprising: —a plurality of zigzag-shaped first spacers extending in a first longitudinal direction, each first spacer comprising at each corner thereof a first loop; —a plurality of zigzag-shaped second spacers extending in the first longitudinal direction, each second spacer comprising at each corner thereof a second loop, each second loop having outer dimensions that are smaller than the inner dimensions of each first loop, —wherein the second loops of each second spacer extend through the first loops of an adjacent first spacer; —wherein the openings defined by the second loops of successive second spacers are registered in rows extending in a second longitudinal direction, which second longitudinal direction extends under an angle of at least 20° with respect to the first longitudinal direction; and—wherein the first spacers and the second spacers define a second zigzag-shape in the second longitudinal direction; —two skin layers arranged on opposite sides of the core, wherein each skin layer comprises a plurality of openings through which the second loops extend; —a plurality of rods, each rod extending through the openings of the second loops of each row at the outer surface of each skin layer such that each rod locks the second loops in the first loops with respect to the skin layer. The invention further relates to a method of building such a sandwich panel, a core of such a sandwich panel, and a building built of a plurality of such sandwich panels.

The invention relates to a sandwich panel comprising a core and two skinlayers arranged on opposite sides of the core. Such a sandwich panel isknown per se.

It is an object of the invention to provide a sandwich panel that allowsfor easy assembling of the core and the two skin layers, such that saidcore and said two skin layers may be transported in a disassembled stateand to be easily assembled on site.

In order to accomplish that objective, the sandwich panel according tothe invention comprises:

-   -   a core, comprising:        -   a plurality of zigzag-shaped first spacers extending in a            first longitudinal direction, each first spacer comprising            at each corner thereof a first loop;        -   a plurality of zigzag-shaped second spacers extending in the            first longitudinal direction, each second spacer comprising            at each corner thereof a second loop, each second loop            having outer dimensions that are smaller than the inner            dimensions of each first loop,        -   wherein the second loops of each second spacer extend            through the first loops of an adjacent first spacer;        -   wherein the openings defined by the second loops of            successive second spacers are registered in rows extending            in a second longitudinal direction, which second            longitudinal direction extends under an angle of at least            20° with respect to the first longitudinal direction; and        -   wherein the first spacers and the second spacers define a            second zigzag-shape in the second longitudinal direction;    -   two skin layers arranged on opposite sides of the core, wherein        each skin layer comprises a plurality of openings through which        the second loops extend;    -   a plurality of rods, each rod extending through the openings of        the second loops of each row at the outer surface of each skin        layer such that each rod locks the second loops in the first        loops with respect to the skin layer.

The sandwich panel according to the invention allows for easy assemblingby arranging the skin layers on opposite sides of the core and by thenplacing the rods through the rows of second loops.

The sandwich panel according to the invention may be used as, but notlimited to, a wall or a roof of a construction or (emergency) building,such as a house, an office building, a garage, a storage shed, astadium, a stable, a quay, a dam, a sewer drain, a swimming pool, etc,or as a bower, a sound wall, a (decorative or protective) (garden)fence, a grandstand, a presentation wall, a display, a bike park, astage, as a building toy optionally for educational purposes, or as partof a bridge (head), of a viaduct, of the casco of a house-boat, etc.

The core may for example be manufactured from a material from the groupcomprising metal, such as iron or (stainless) steel, and (fibrereinforced) plastic or composite material.

Practically the angle is approximately 90°.

In an embodiment of the sandwich panel according to the invention, saidsandwich panel comprises limitation means for limiting the distance bywhich each second loop extends through each first loop and/or by whicheach second loop extends through each opening in each skin layer.

The second spacer and/or the first spacer may comprise said limitationmeans, said limitation means comprising two elongated elements extendingin the first longitudinal direction, which elongated elements mutuallyconnect the second loops on each longitudinal side of the second spacerand/or which elongated elements mutually connect the first loops on eachlongitudinal side of the first spacer.

The elongated elements have the further advantage of clearly definingthe location of the first loops and the second loops in the firstlongitudinal direction, such that the location of the openings of theskin layers may be easily be adapted thereto.

Practically the angle of the first loop with respect to the longitudinalplane of the first spacer lies in the range of between 90° to 150°.

An angle of approximately 90° has the advantage that the core of thesandwich panel is foldable to a folded up first state in which the corehas a more or less flat shape, such that the core requires relativesmall space, which is convenient for, for example, transport andstorage. At a building site the core is easily expandable to itsexpanded state, in which the core functions as a spacer for the sandwichpanel.

When the size of the openings of the skin layers is smaller than thesize of the first loops, such that the first loops cannot extend throughthe openings of the skin layers, this angle of the first loop withrespect to the longitudinal plane of the first spacer limits the maximumangle of the longitudinal plane of the first spacer with respect to theskin layers, which maximum angle is obtained when the first loops extendparallel to the skin layers. By choosing an appropriate angle of thefirst loop with respect to the longitudinal plane of the first spacer,the maximum angle of the longitudinal plane of the first spacer withrespect to the skin layers is defined as 180° minus the angle of thefirst loop with respect to the longitudinal plane of the first spacer.Thus the maximum angle is approximately 60°, respectively approximately45°, if the angle of the first loop with respect to the longitudinalplane of the first spacer is approximately 120°, respectivelyapproximately 135°.

The angle of the first loop with respect to the skin layer may lye inthe range of between 0° to 45°.

An angle of the second loop with respect to the longitudinal plane ofthe second spacer may lye in the range of between 120° to 180°.

The angle of the second loop with respect to the skin layer ispreferably approximately 90°, such that the rods may easily be placedthrough the openings of the second loops.

With the angle of the second loop with respect to the skin layer beingpreferably approximately 90° and the angle of the second loop withrespect to the longitudinal plane of the first spacer being in the rangeof between 120° to 180°, an angle between the longitudinal plane of thesecond spacer and the skin layers is between 120° to 180° minusapproximately 90°, i.e. between 30° to 90°.

Preferably, the angle of the longitudinal plane of the first spacerand/or the angle of the longitudinal plane of the second spacer withrespect to the skin layers lies in the range of between 30° to 90°.These angles may be equal or different for the first spacers and thesecond spacers.

All angles may be chosen in accordance with required strength of thesandwich panel, and in accordance with desired dimensions of thesandwich panel.

In an embodiment of the sandwich panel according to the invention, atleast one of the two skin layers is a mesh.

Such a mesh has the advantage that it comprises more openings than thecore comprises second loops, such that the second loops may easily beplaced through the openings of the mesh. Also, such a mesh is relativelycheap.

The mesh may for example be made from a material from the groupcomprising metal, such as iron or (stainless) steel and (fibrereinforced) plastic or composite material.

A sandwich panel comprising such mesh skin layers may for example befilled with rocks and mud and may for example be used as a noiseprotection wall that may for example be located along roads in urbanareas.

Also, such a sandwich panel may conveniently be used for building housesand other buildings, such as stores and offices, in area's that havesuffered from a natural disaster, such as an earth quake. The brokenbricks and other remainings of collapsed buildings may be used as afilling material for filling up the core of the sandwich panel, suchthat new buildings may be made relatively easy and fast. Thus, thepeople living in said area may have new homes relatively fast. Suchhomes may be temporally, wherein more permanent buildings may be builtwhile the people are living in homes comprising the sandwich panelsaccording to the invention. After finishing the more permanentbuildings, said temporally homes and buildings may easily bedisassembled by removing first the rods, then the skin layers, and bythen folding up or dismounting the core. The sandwich panels may then bereused used at a different location. For such an application, it isconvenient if the core, skin layers and rods are transported to thenatural disaster area in a disassembled state and being assembled onsite. Said core is preferable transported in its folded up state.

After filling the panel with mesh skin layers, for example with rubble,luting with concrete may take place. This way, a relatively cheap andlow-weight water tight construction element may be formed, which can beused for any of the above described purposes. Alternatively oradditionally, at least one of the two skin layers may be a panel.

Such a panel has the advantage, that the core and/or the optionalfilling of the core of the sandwich panel, is at least less visible fromthe outside. The thickness of the panel may be chosen as desired.

The panel may for example be made from a material from the groupcomprising wood, metal, such as iron or (stainless) steel and (fibrereinforced) plastic or composite material.

Alternatively or additionally, at least one of the two skin layers maybe a sandwich panel, comprising a core and two skin layers, wherein thecore and an inner skin layer of the two skin layers comprise saidplurality of openings and wherein the outer skin layer covers saidplurality of openings.

Such a sandwich panel skin layer has the advantage, that the outer skinlayer covers said plurality of openings and the second loops and rodslocated therein. Thus, the openings, second loops and rods are notvisible from the outside. The outer skin layers may for example comprisea finishing layer, such as finish plaster, wood, tiles, bricks or thelike, such that after assembly of the sandwich panel 1000 no furtherfinishing is required. One of the finishing layers of the outer skinlayers may for example be watertight, such that the sandwich panel maybe used as an outer wall of a building, also in areas where rain occurs.The core may for example be made of a noise or energy isolating layer,such as polyurethane (PUR).

Since the loops are not visible from the outside, practically saidsandwich panel comprises guiding means provided in the core of saidsandwich panel skin layer for guiding the rods through said secondloops.

Said guiding means may for example comprise guiding pipes or tubes.

The sandwich panels comprising panels as skin layers or sandwich panelsas skin layers may also be used for building buildings, such as houses,stores and offices. For example as temporary buildings in areas thathave suffered from a natural disaster, as well as more permanentbuildings in all areas.

The invention also relates to a method of building a sandwich panelaccording to any of the preceding claims, comprising the steps of:

a) building a core, comprising the steps of:

-   -   providing a plurality of zigzag-shaped first spacers extending        in a first longitudinal direction, each first spacer comprising        at each corner thereof a first loop;    -   providing a plurality of zigzag-shaped second spacers extending        in the first longitudinal direction, each second spacer        comprising at each corner thereof a second loop, each second        loop having outer dimensions that are smaller than the inner        dimensions of each first loop,    -   placing the second loops of each second spacer through the first        loops of an adjacent first spacer, wherein the openings defined        by the second loops of successive second spacers are registered        in rows extending in a second longitudinal direction, which        second longitudinal direction extends under an angle of at least        20° with respect to the first longitudinal direction, and        wherein the first spacers and the second spacers define a second        zigzag-shape in the second longitudinal direction; and

b) arranging two skin layers on opposite sides of the core by placingthe second loops of the core through openings of the skin layers;

c) placing a plurality of rods through the openings of the second loopsof each row at the outer surface of each skin layer such that each rodlocks the second loops in the first loops with respect to the skinlayer.

With such a method the sandwich panel may be built relatively easy andfast. Also, the sandwich panel may easily and/or fast be dismantled byreversing the steps.

The invention further relates to a core of a sandwich panel, said corecomprising:

-   -   a plurality of zigzag-shaped first spacers extending in a first        longitudinal direction, each first spacer comprising at each        corner thereof a first loop;    -   a plurality of zigzag-shaped second spacers extending in the        first longitudinal direction, each second spacer comprising at        each corner thereof a second loop, each second loop having outer        dimensions that are smaller than the inner dimensions of each        first loop,    -   wherein the second loops of each second spacer extend through        the first loops of an adjacent first spacer;    -   wherein the openings defined by the second loops of successive        second spacers are registered in rows extending in a second        longitudinal direction, which second longitudinal direction        extends under an angle of at least 20° with respect to the first        longitudinal direction; and    -   wherein the first spacers and the second spacers define a second        zigzag-shape in the second longitudinal direction.

The core may further comprise the features as described with respect tothe sandwich panel that relate to said core.

Preferably, the core is foldable between a folded up first state and anexpanded second state.

In the folded up first state the core requires less space than in theexpanded second state, such that the core may easily be transported andstored in the folded up first state. At a building the core may easilybe expanded to its expanded state. Dependent on the angle of the firstloop with respect to the longitudinal plane of the first spacer, thecore may have a more or less flat shape in the folded up state.

The invention also relates to buildings built using a plurality ofsandwich panels according to the invention. Such buildings may be builtrelatively easy and fast and may conveniently be used in any area, inparticular in areas that have suffered from a natural disaster. Meansfor mutually connecting a plurality of the sandwich panels may beprovided. The sandwich panels may be used as walls, roofs, floors, orany desired part of the building.

The invention will now be explained in more detail with reference tofigures illustrated in a drawing, wherein:

FIG. 1 shows a part of a sandwich panel according to a first embodimentof the invention;

FIG. 2 shows the sandwich panel of FIG. 1 in an exploded view;

FIG. 3 shows a detailed view of the core of the sandwich panel of FIG.1;

FIGS. 4A and 4B show a first spacer (A) and a second spacer (B) of thecore of the sandwich panel of FIG. 1;

FIG. 5 is a side view of a first assembling method of the sandwich panelof FIG. 1;

FIG. 6 shows a sandwich panel according to a second embodiment of theinvention;

FIG. 7 shows the sandwich panel of FIG. 6 in an exploded view;

FIGS. 8A and 8B show a sandwich panel according to a third embodiment ofthe invention;

FIGS. 9A and 9B show a first spacer (A) and a second spacer (B)according to a second embodiment of the spacer according to theinvention;

FIGS. 10A-10C are a side view of a second assembling method of the coreof the sandwich panel of FIG. 1; and

FIGS. 11A-11C are a side view of the second assembling method of a coreaccording to a further embodiment of the invention;

FIGS. 12A, 12B show cores according to a further embodiment of theinvention in the expanded second state of FIGS. 10C and 11C,respectively.

FIGS. 1, 2 and 3 show a sandwich panel 1 according to a first embodimentof the invention, which sandwich panel comprises a core 2, two skinlayers 3A, 3B, a plurality of rods 4, and four side panels 5A-5D.

The core 2 comprises a plurality of zigzag-shaped first spacers 6, whichfirst spacers 6 extend in a first longitudinal direction 8. Each firstspacer 6 comprises at each corner thereof a first loop 9. The firstloops extend parallel with respect to the skin layers 3A, 3B and underan angle 25 of approximately 120° with respect to a longitudinal planeof the first spacer 6 (see FIG. 5).

The core 2 further comprises a plurality of zigzag-shaped second spacers7, which also extend in the first longitudinal direction 8. Each secondspacer 7 comprises at each corner thereof a second loop 10, wherein theouter dimensions of the second loops 10 are smaller than the innerdimensions of each first loop 9, such that the second loops 10 mayextend through the first loops 9. The second loops 10 extendperpendicular with respect to the skin layers 3A, 3B and under an angle26 of approximately 150° with respect to a longitudinal plane of thesecond spacer 7, see FIG. 5.

At the side zones of the core 2, said core 2 comprises a second type ofsecond spacer 19, as is seen in FIGS. 1 and 3. This second type ofsecond spacer 19 differs from the first type second spacer 7 only inthat the second loops 20 extend in the same direction as thelongitudinal plane of the second type second spacer 19, such that thesecond type second spacer 19 extends perpendicular with respect to saidskin layers 3A,3B. Thus, the angle 26 of the second type second spaceris 180°, instead of 150°.

As is clear from FIG. 3, the second loops 10 of each second spacer 7extend through the first loops 9 of an adjacent first spacer 6, suchthat the first spacers 6 and the second spacers 7 define a secondzigzag-shape in a second longitudinal direction 11, which secondlongitudinal direction 11 extends under an angle of 90° with respect tothe first longitudinal direction 8. In FIG. 3, the first longitudinaldirection 8 of the zigzag-shapes of the first spacers 6 and the secondspacers 7,19 is elucidated by the black colour of the second type secondspacer 19. The second longitudinal direction 11 of the zigzag-shapedefined by the coupled first spacers 6 and second spacers 7 iselucidated by the dashed upper bars of the first and second spacers6,7,19.

As is further clear from FIG. 3, only at one side of the second typesecond spacer 19 do the second loops 20 extend through the first loops 9of the first spacer 6. At the other side of the second type secondspacer 19 the second loops 20 extend only through the openings 13 ofskin layer, see FIG. 1. This is the result of the second type secondspacer 19 being the outer second spacer.

As is further clear from FIG. 3, the openings 12 defined by the secondloops 10, 20 of successive second spacers 7,19 are registered in rowsextending in the second longitudinal direction 11, such that the rods 4can be placed through the second loops 10, 20.

The skin layers 3A, 3B are arranged on opposite sides of the core 2,wherein each skin layer 3A, 3B is a mesh comprising a plurality ofopenings 13 through which the second loops 10,20 extend.

As is clear from FIG. 1, the rods 4 extend through the openings 12 ofthe second loops 10,20 of each row at the outer surface of each skinlayer 3A, 3B such that each rod 4 locks the second loops 10,20 in thefirst loops 9 with respect to the skin layer 3A, 3B.

The side panels 5A-5D are also a mesh comprising openings 14. Each mesh5A-5D comprises edge zones 15 extending under an angle of 90° withrespect of a main plane of the panels 5A-5D, such that the edge zones 15extend parallel with respect tot the skin layers 3A, 3B. The secondloops 10,20 that are located at the outer zones of the core 2 extendthrough the openings 14 of the edge zones 15 of the panels 5A-5D and therods 4 extend through the openings 12 of the second loops 10,20 at theouter surface of the edge zones 15 of the panels 5A-5D, such that eachrod 4 locks the second loops 10,20 in the first loops 9 with respect tothe skin layer 3A, 3B and the side panels 5A-5D.

As is clear from FIG. 3, each spacer 6,7 comprises two elongatedelements 16,17 extending in the first longitudinal direction 8. Theelongated elements 16,17 are fixedly mounted to the corners of eachspacer 6,7 at each longitudinal side of the spacers 6,7, and thus at thelocations from which the loops 9,10 extend. As such, the elongatedelements 16,17 mutually connect the loops 9,10 at each side of thespacers 6,7. As a result of the elongated elements 16,17 the locationsof the loops 9,10 with respect to the first longitudinal direction 8 areclearly defined, such that the locations of the openings of the skinlayers 3A, 3B and the side panels 5A-5D may easily be adapted thereto.This is especially important if the skin layer is a skin layer accordingto FIGS. 6-8, as will be explained later. The elongated elements 17 ofthe second spacer 7 limit the distance by which each second loop 10extends through each first loop 9 and the elongated elements 16 of thefirst spacer 6 limit the distance by which each second loop 10 extendsthrough each opening 13 in each skin layer 3A,3B by preventing the firstloops 9 from extending through the openings 13. The second type secondspacer 19 comprises elongate elements 28, also extending in the firstlongitudinal direction 8, which elongated elements 28 mutually connectthe loops 20 at each longitudinal side of the second type second spacer19.

FIG. 4A shows a perspective view of the first spacer 6. This figureclearly shows the elongated elements 16 extending in the firstlongitudinal direction 8 and connecting the loops 9. FIG. 4A furthershows the angle 21 of the zigzag-shape, which is approximately 60°. Theangle 22 of the outer zigzag is half the angle 21, which is thusapproximately 30°. The outer zigzag thus extends in a plane that isperpendicular to the skin layers 3A,3B.

FIG. 4B shows a perspective view of the second spacer 7. This figureclearly shows the elongated elements 17 extending in the firstlongitudinal direction 8 and connecting the loops 10. FIG. 4B furthershows the angle 23 of the zigzag-shape, which is approximately 60°. Theangle 24 of the outer zigzag is half the angle 23, which is thusapproximately 30°. The outer zigzag thus extends in a plane that isperpendicular to the skin layers 3A,3B.

FIG. 5 shows in detail how the sandwich panel is assembled. Each secondspacer 7 is coupled to a first spacer 6 and the skin layer 3A, byplacing the second loop 10 in the first loop 9 and in the opening 13 ofthe skin layer 3A. Once the second loop 10 extends through the firstloop 9 and the opening 13 of the skin layer 3A, a rod 4 is placedthrough the registered openings 12 of the second loops 10 at the outersurface of the skin layer 3A, such that the rod 4 locks the second loops10 in the first loops 9 with respect to the skin layer 3A, 3B.

As described above, FIG. 5 shows the angles 25, 26 of the loops 9,10with respect to the longitudinal planes of the spacers 6,7, which angles25,26 are respectively 120° and 150°. An angle 27 of the longitudinalplanes of the spacers 6,7 with respect to the skin layers 3A, 3B is 60°,such that also the angle 29 between the longitudinal planes of thespacers 6,7 is 60°. Dependent on the required strength of the sandwichpanel 1 and the desired distance between the skin layers 3A,3B, theangles 25,26,27 may be chosen differently.

The second type second spacer 19 is not disclosed in FIG. 5. Asdescribed above, the angle 26 of the second type second spacer 19 is180° and the loops 20 extend perpendicular with respect to the skinlayers 3A,3B, such that the angle 27 of the longitudinal plane of thesecond type second spacer 19 with respect to the skin layers 3A, 3B is90°.

FIGS. 6, 7 show a second embodiment of a sandwich panel 100. The core 2of the sandwich panel 100 is the same core 2 of the sandwich panel ofFIGS. 1-5 and is described above, wherein the same numbers refer to thesame above described features. The skin layers 103A,103B differ from theskin layers 3A,3B of FIG. 1,2 in that the skin layers 103A,103B are notmeshes, but panels comprising openings 113. The number and location ofthe openings 113 of the skin layers 103A,103B are adapted to the numberand location of the second loops 10,20 of the core 2. As describedabove, as a result of the elongated elements 16,17,28 the locations ofthe loops 9,10,20 in the first longitudinal direction 8 are clearlydefined, such that the locations of the openings 113 of the skin layers103A, 103B may easily be adapted thereto. This is important because theskin layers 103A,103B have openings 113 only at the location of thesecond loops 10,20, and thus the same number of openings 113 as thenumber of second loops 10,20, which is different to the mesh skin layers3A,3B, which comprise much more openings 113 than the core 2 comprisessecond loops 10,20.

As is clear from FIGS. 6, 7, the first longitudinal direction 8 nowextends horizontal and the second longitudinal 11 now extends vertical,which is opposite to FIGS. 1-5, in which FIGS. 1-5 the firstlongitudinal direction 8 extends vertical and the second longitudinaldirection 11 extends horizontal. It is therefore clear for the skilledperson that the orientation of the core 2 is unimportant. For practicalreasons the orientation of the core 2 of FIGS. 6,7 may be chosen whenthe height of the sandwich panel 100 is relatively low, such that therods 4 may easily be placed from above through the registered openings12 of the loops 10,20 of the second spacers 7,19.

FIGS. 8A and 8B show a second embodiment of a sandwich panel 1000. Thecore 2 of the sandwich panel 1000 is the same core 2 of the sandwichpanel of FIGS. 1-5 and is described above, wherein the same numbersrefer to the same above described features. The skin layers 1003A,1003Bdiffer from the skin layers 3A,3B of FIG. 1,2 and the skin layers103A,103B of FIGS. 6,7 in that the skin layers 103A,103B are sandwichpanels. The sandwich panels 1003A,1003B comprise openings 1013 thatextend only through the inner skin layers 1030, which inner skin layers1030 are directed to the core 2 of the sandwich panel 1000, and the core1031 of the sandwich panels 1003A,1003B. The outer skin layers 1032cover the openings 1013, such that the openings 1013, the loops 10,20and the rods 4 are not visible from the outside. The outer skin layers1032 may for example comprise a finishing layer, such as finish plaster,wood, tiles, bricks or the like, such that after assembly of thesandwich panel 1000 no further finishing is required. One of thefinishing layers of the outer skin layers 1032 may for example bewatertight, such that the sandwich panel 1000 may be used as an outerwall of a building. The core 1031 may for example be made of a noise orenergy isolating layer, such as polyurethane (PUR).

As is seen in FIG. 8B, pipes 1033 extend in rows in the secondlongitudinal direction 11 through the core 1031 of the sandwich panels1003A,1003B over the total length of the sandwich panels 1003A,1003B.The pipes 1033 extend from each opening 1013 to a next opening 1013, butnot through the opening 1013, such that the second loops 10,20 can beplaced in the openings 1013. The pipes 1033 serve as guiding means forthe rods 4, wherein the rods 4 may be placed in the pipes 1033 from theouter end zones of the sandwich panels 1003A,1003B. Such guiding means1033 are convenient, because, as described above, the loops 10,20 arenot visible from the outside due to the presence of the outer skinlayers 1032 and thus enhance the placing of the rods 4 through thesecond loops 10,20.

FIGS. 9A and 9B show second embodiments of the first and second spacers106,107 comprising respective first loops 109 and second loops 110. Thefirst and second spacers 106,107 of FIGS. 9A, 9B differ from the firstand second spacers 6,7 of FIGS. 4A, 4B only in that the first and secondspacers 106,107 do not comprise said elongated elements. Such first andsecond spacers 106,107 may be applied if the location of the openings ofthe skin layers of the sandwich panel is not critical, for example whenthe skin layers are the meshes of FIGS. 1,2 and/or when the skin layeritself provides sufficient strength and stability.

FIGS. 10A-10C are a side view of a second assembling method of the core2 of the sandwich panels 1,100,1000 of FIGS. 1-8. From these FIGS.10A-10C it is clear that the core 2 is foldable between a folded upfirst state (FIG. 10A) and an expanded second state (FIG. 10C). FIG. 10Bshows an intermediate state. In the folded up first state the core 2requires less space as compared to the expanded second state, which isconvenient for transport and storage of the core 2. At a building sitethe core 2 may be folded from the first state to its expanded secondstate and then coupled to the skin layers 3A,3B,103A,103B,1003A,1003B byplacing the rods 4 through the second loops 10,20. The first and secondspacers 6,7,19 stay mutually connected during the folding of the core 2by means of said loops 9,10,20, such that folding between the first andsecond states may take place relatively easy and fast.

FIGS. 11A-11C are a side view of the second assembling method of afurther core 102 according to the invention. The core 102 differs fromthe core 2 of FIGS. 1-8 in that the angle 125 between the loop 109 ofthe first spacer 106 and the longitudinal plane of the first spacer 106is 90° instead of 120°. As a result of the angle 125 being 90°, thelongitudinal planes of the first and second spacers 106,107 extendparallel in the folded up first state of FIG. 11A. As such, the core 102has a more or less flat shape in the folded up state and thus requiresmuch less space in the folded up first state as compared to the expandedsecond state of the core 102 as shown in FIG. 11C. FIG. 11B shows anintermediate state. It is noted that the second spacer 107 of the core102 is equal to the second spacer 7 of the core 2 of FIGS. 1-8. Thesecond type second spacer 19 is not disclosed in FIGS. 11A-11C and isalso equal to the second type second spacer of the core 2 of FIGS. 1-8.As described above with respect to FIGS. 10A-10C, the first and secondspacers 106,107,19 stay mutually connected during the folding of thecore 2 by means of said loops 109,110,20, such that folding between thefirst and second states may take place relatively easy and fast.

In order to prevent the first spacers 6;106 and the second spacers7,19;107,19 from uncoupling during folding, coupling means in the formof a wires, tapes or belts may be provided that connect each first loop9;109 of a first spacer 6;106 to a second loop 10,20;110,20 of anadjacent second spacers 7,19;107,19 together and as such preventuncoupling. The wires, tapes or belts may also be provided around eachpair of elongated elements 16,17,28 of each pair of adjacent firstspacers 6;106 and second spacers 7,19;107,19.

As is clear from FIG. 11C, as a result of the angle 125 being 90°, thefirst loop 109 does not extend parallel to the skin layer of thesandwich panel.

FIGS. 12A; 12B show cores 2; 102 in the expanded state of FIGS. 10C;12C, respectively, which cores 2; 102 differ from the cores of FIGS.10A-10C; 11A-11C in that the first spacers 6; 106 comprise an abutment40; 140, which abutments 40; 140 limit the maximum angle between thelongitudinal planes of the first and second spacers 6,7; 106,107 in theexpanded second state. The maximum angle between the longitudinal planesof the first and second spacers 6,7; 106,107 in the expanded secondstate is preferably 60°, see also FIG. 5 in which this angle is denotedby reference numeral 29. The abutments 40; 140 are formed by bendedportions of the first loops 9; 109 on both sides of the first spacers 6;106.

The invention is not restricted to the variants shown in the drawing,but it also extends to other preferred embodiments that fall within thescope of the appended claims.

In this respect it is noted that all disclosed angles may be chosen asdesired and in dependence of required strength and size of the sandwichpanel. In particular the angle 27 between the longitudinal planes of thefirst and second spacers 6;106,7;107 and the skin layers3A;103A;1003A,3B;103B;1003B may be variable and may be fixated byplacing the second loops 10;110 through an opening of the skin layers3A;103A;1003A,3B;103B;1003B and by then placing the rod through thesecond loops 10;110.

1. A sandwich panel, comprising: a core, comprising: a plurality ofzigzag-shaped first spacers extending in a first longitudinal direction,each first spacer comprising at each corner thereof a first loop; aplurality of zigzag-shaped second spacers extending in the firstlongitudinal direction, each second spacer comprising at each cornerthereof a second loop, each second loop having outer dimensions that aresmaller than the inner dimensions of each first loop, wherein the secondloops of each second spacer extend through the first loops of anadjacent first spacer; wherein the openings defined by the second loopsof successive second spacers are registered in rows extending in asecond longitudinal direction, which second longitudinal directionextends under an angle of at least 20° with respect to the firstlongitudinal direction; and wherein the first spacers and the secondspacers define a second zigzag-shape in the second longitudinaldirection; two skin layers arranged on opposite sides of the core,wherein each skin layer comprises a plurality of openings through whichthe second loops extend; a plurality of rods, each rod extending throughthe openings of the second loops of each row at the outer surface ofeach skin layer such that each rod locks the second loops in the firstloops with respect to the skin layer.
 2. The sandwich panel according toclaim 1, wherein the angle is approximately 90°.
 3. The sandwich panelaccording to claim 1, comprising a limiter configured for limiting thedistance by which each second loop extends through each first loopand/or by which each second loop extends through each opening in eachskin layer.
 4. The sandwich panel according to claim 3, wherein thesecond spacer and/or the first spacer comprise(s) said limiter, saidlimiter comprising two elongated elements extending in the firstlongitudinal direction, which elongated elements mutually connect thesecond loops on each longitudinal side of the second spacer and/or whichelongated elements mutually connect the first loops on each longitudinalside of the first spacer.
 5. The sandwich panel according to claim 1,wherein an angle of the first loop with respect to the longitudinalplane of the first spacer lies in the range of between 90° to 150°. 6.The sandwich panel according to claim 1, wherein an angle of the firstloop with respect to the skin layer lies in the range of between 0° to45°
 7. The sandwich panel according to claim 1, wherein an angle of thesecond loop with respect to the longitudinal plane of the second spacerlies in the range of between 120° to 180°.
 8. The sandwich panelaccording to claim 1, wherein an angle of the longitudinal plane of thefirst spacer and/or an angle of the longitudinal plane of the secondspacer with respect to the skin layers lies in the range of between 30°to 90°.
 9. The sandwich panel according to claim 1, wherein at least oneof the two skin layers is a mesh.
 10. The sandwich panel according toclaim 1, wherein at least one of the two skin layers is a panel.
 11. Thesandwich panel according to claim 1, wherein at least one of the twoskin layers is a sandwich panel, comprising a core and two skin layers,wherein the core and an inner skin layer of the two skin layers comprisesaid plurality of openings and wherein the outer skin layer covers saidplurality of openings.
 12. The sandwich panel according to claim 11,comprising guiding means provided in the core of said sandwich panelskin layer for guiding the rods through said second loops.
 13. A methodof building a sandwich panel, the method comprising: a) building a core,comprising the steps of: providing a plurality of zigzag-shaped firstspacers extending in a first longitudinal direction, each first spacercomprising at each corner thereof a first loop; providing a plurality ofzigzag-shaped second spacers extending in the first longitudinaldirection, each second spacer comprising at each corner thereof a secondloop, each second loop having outer dimensions that are smaller than theinner dimensions of each first loop, placing the second loops of eachsecond spacer through the first loops of an adjacent first spacer,wherein the openings defined by the second loops of successive secondspacers are registered in rows extending in a second longitudinaldirection, which second longitudinal direction extends under an angle ofat least 20° with respect to the first longitudinal direction, andwherein the first spacers and the second spacers define a secondzigzag-shape in the second longitudinal direction; and b) arranging twoskin layers on opposite sides of the core by placing the second loops ofthe core through openings of the skin layers; c) placing a plurality ofrods through the openings of the second loops of each row at the outersurface of each skin layer such that each rod locks the second loops inthe first loops with respect to the skin layer.
 14. An element, saidelement comprising: a plurality of zigzag-shaped first spacers extendingin a first longitudinal direction, each first spacer comprising at eachcorner thereof a first loop; a plurality of zigzag-shaped second spacersextending in the first longitudinal direction, each second spacercomprising at each corner thereof a second loop, each second loop havingouter dimensions that are smaller than the inner dimensions of eachfirst loop, wherein the second loops of each second spacer extendthrough the first loops of an adjacent first spacer; wherein theopenings defined by the second loops of successive second spacers areregistered in rows extending in a second longitudinal direction, whichsecond longitudinal direction extends under an angle of at least 20°with respect to the first longitudinal direction; and wherein the firstspacers and the second spacers define a second zigzag-shape in thesecond longitudinal direction.
 15. The element according to claim 12,wherein the element is foldable between a folded up first state and anexpanded second state.